Maci Bookout chronicled her teen pregnancy with son Bentley on the inaugural episode of "16 and Pregnant" and, through the years, documented her journey as a young parent on "Teen Mom." From Benny's birth to his first day at school, we've watched their heartwarming relationship unfold -- and seen our fair share of wonderful interactions between the MTV duo.

Now, the MTV cast member is expecting baby No. 2 with longtime boyfriend Taylor McKinney -- Bentley is going to be a big bro! -- and there are plenty more milestone experiences in store for Maci as well as her loved ones.

To celebrate the redhead's second pregnancy, look back at some of Maci and Bentley's most memorable experiences together:

Hello, Bentley!

Even though the Tennessee native said that giving birth was the "hardest thing she's done" -- she was in labor for more than 30 hours! -- there was no denying her sheer joy when she proudly held a swaddled Baby B for the very first time.

Graduation buddies

Shortly after welcoming Bentley, Maci donned her cap and gown -- an incredible feat considering most teen moms don't complete high school -- and her newborn slept cheered her on along with her many family and dear friends. You get that diploma, girl!

"Will you be my Valentine for life?"

Maci offered her perfect sweetheart pink and blue candies -- and plenty of kisses -- during the February holiday.

Birthday boy

What's better than a bouncy house and cake?!

"I want mommy!"

Maci worried that her little guy wasn't spending enough time with other kids, so she decided to enroll him in daycare. Initially, the toddler enjoyed the activities with the other youngins' (that smile during the sing-a-long!), but when it was time for his mama to leave, he had a very difficult time adjusting.

Splish-splash

At first, the tot was a bit resistant to getting in the water and learning how to swim without the support of Maci and her then-boyfriend Kyle, who sat on the sidelines. Eventually, thanks to his supportive mama, B got comfortable in the pool and was grinning as he took a triumphant trip down the slide.

Preschool, here we come!

Bentley shed a few tears when he made his way into the classroom -- normal growing pains for any first-day student. But after a few tough minutes, the undeniably charming kiddo eased into the day.

Motorbiking extraordinaire

Maci and Bentley's dad Ryan treated their son to an adventure at the park, and the youngster showed off his skills to his proud 'rents.

+ What's your favorite Maci and Bentley moment? Let us know in the comments, and be sure to stay with MTV News for more updates on Maci's pregnancy -- plus her MTV return!